This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
In a cellular wireless communication system, for example a Long Term Evolution (LTE) system, a terminal device moves from one cell to another. A mobility procedure is defined for specifying operations of the terminal device (e.g., a user equipment, or UE) and base stations (BSs) to support the mobility. In LTE systems, an active mode mobility procedure as shown in FIG. 1 is defined, for specifying signaling exchanges between an active mode UE and base stations which are also called evolved NodeBs or eNBs in LTE, and interacting between the base stations to support a handover of the UE. As shown in FIG. 1, UE measures signal quality (for example, reference signal receiving power (RSRP)) of its serving cell and neighboring cells based on cell-specific reference signals (CRSs). The UE will send a measurement report to its serving eNB following a predefined criterion, for example, the UE will send the measurement report if a signal quality of a neighbor cell is better than that of its serving cell by a preconfigured offset. Based on the measurement report, the serving eNB is aware of the best cell for the UE. If the best cell is not the current serving cell, the serving eNB can notify the UE to handover to the best cell.
In a next generation or fifth generation (NX/5G) wireless system being discussed, for example in the third generation partnership project (3GPP), there is no concept of cell anymore. A terminal device is within coverage of a beam, and mobility means that the terminal device moves from one beam controlled by an access node (AN) to another beam controlled by the same AN or a different AN node.